Laptop fan doesn't turn on

[COLOR="#0000FF"]From what I can tell, my laptop fan has stopped turning on when I start my computer. I say this because I hear a humming, but the computer still turns off, and when my fan actually is on to my knowledge, it's super loud. Before this, it wouldn't come on every once in a while, and I would have to turn off and on, or let it turn off for me because I didn't notice. Now the fan rarely comes on, and the only reason I can say rarely is because it recently came on yesterday.

I thought the dirt in the fan might be making it stop, and since it has gotten noisier, I was sure this was the problem. After cleaning the fan out, the fan didn't turn on at the first boot. Waited like 3 hours (mostly watching tv while being depressed), then decided to turn it on, and to my surprise, it worked, but still as loud as ever, even with a cleaned fan. Today the fan hasn't come on, which makes me wonder what the problem is.
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i had some of the symptoms above with my old power supplier: i have a desktop, it had no problem turning on but the power supplier's fan made a lot of noise, even after i cleaned the dust (the same as you thought), and recently, when it began making loud noises every ~20 minutes after the startup itself ( it made noises on startup too ) i decided to take it to a technician, and he checked it and said that the power supplier is dead(the computer was still working).
i don't really know about laptops, but if the laptop doesn't even turn on (you didn't say if you use the battery while trying to turn it on, so i'll take this case as it's without a battery) the power supplier might be dead, but remember, i dont really know a lot of laptops, and in the advice i gave i mean that even pressing the power button to turn on the laptop doesn't do make the computer even turn on and show SOMETHING.
maybe what VerrKol says is right, but that can happen in the case that the computer does turn on.
i hope this will help you somehow :3

oh, and i might have an advice for you: try turn it on without the battery and see if it works (in case you haven't tried that), but i don't think the battery has anything to do with the noise of the fan.